Resin-forming composition for stabilization of soil and process of using same



i ma' yla" United States Patent RESIN-FORMING COMPOSITION FOR STABILIZA- TION F SOIL AND PROCESS OF USING SAME Russell Morgan, Riverside, and John J. Padbury, Old Greenwich, Conn, assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine N0 Drawing. Application August 15, 1955,

. Serial No. 528,542

21 Claims. (Cl. 260-41) This invention rel-ates to soil stabilization by which soil is rendered less permeable to the passage of inert liquids or cohered to improve its load-bearing qualities.

This application is a continuation-in-part of our application Serial No. 236,454, filed July 12, 1951, now abandoned.

For many years great difficulty has been experienced in the construction of roadways and airfields on certain types of soil, such as the various clays, which form very fluid, gummy mods and are therefore incapable of supporting heavy weight. Similarly, sand is unsuitable for the support of heavy vehicles in many instances. In order to overcome these difliculties, portable steel mats have been used; and, of course, concrete and asphalt roadways and airport runway-s have been extensively employed. These,

have the disadvantage that they require the transportation of large quantities of heavy construction materials, sometimes at great distances and often where there are in adequate means for transportation.

The erosion and permeability characteristics of soil have also presented many continuing problems to engineers. The erosion of and percolation of water through dams and levees constructed of earth have occasionally resulted in disasters and usually require vigilant maintenance with recurring expenditures for reconstruction and repair. Serious problems are also encountered in passages or channels in the earth due to the leakage of water from subterranean springs into tunnel-s or from the normal water table into oil wells through porous strata of the earth. In addition, during drilling, large quantities of valuable oil well drilling muds are lost when the mud under pressure passes from the well out into porous formations, such as shale and sandstone. referred to as lost circulation. At present, steel casings for oil'wells are usually cemented in place in the bore hole with concrete at relatively high cost. Another problem of great magnitude is the seepage of soil water into basements and cellars. This is very difficult to prevent, especially in existing structures except at great expense by rem-oval of all earth from the exterior of the cellar .walls in order to permit the application of waterproofing compositions directly to the exterior masonry walls.

In excavating, and especially in trenching, a loose sandy soil or mud, the excavation must be made much wider than otherwise necessary by reason of adjacent soil falling or sliding back into the trench o-r excavation. -Since this entails the removal of large quantities of additional earth at a greater expense, it would be highly desirable to be able to stabilize the adjacent soil in order that the excavations could be made with substantially vertical walls. Accordingly, there is a real need for soil treatments providing improved strength or lowered permeability to water This is commonly ice lized soil compositions of decreased permeability to inert liquids, particularly water.

A further object of the invention is to provide soil A still further object of the invention is: to cement cas' ings or liners in place in channels in the earth.

Another object of the invention is to stabilize the soil surrounding subterranean foundations or anchors.

A still further object of the invention is to provide soil compositions suitable for use as pseudo-monolithic or integral structures or for molding into individual structural building units.

Still another object of the invention is to stabilize soil against caving in or sliding.

Other objects and advantages of the invention will be apparent tothose skilled in the art upon consideration of the detailed disclosure hereinbel-ow.

The present invention comprises certain compositions which are capable of conversion by or interpolymerization or copolymerization of the polymerizable substances to. a state whereinthe essential final components are not substantially self-dispersible in water (i. e., do not form,

even after appropriate agitation, true or colloidal solutions, emulsions, or suspensions in water in the absence of dispersing agents) to any significant extent, various pros esses by which these compositions are prepared or formed, and the resulting water-insoluble products. The convertible compositions comprise between about 3 and about is :a hydrocarbon residue of an aldehyde and R is of the group consisting of hydrogen and methyl. The other comonomer is any solid, liquid or gaseous ethylenic (i. e., contains at least one radical) compound with a solubility of at least about 2% or both which preferably do not require the removal of the soil from the ground in all applications.

An object of this invention is to provide cohesive soil masses.

An additional object of the invention is to provide stabiby weight, and preferably at least about 5%, in water and which copolymerizes with the aforesaid bisaorylamide in an aqueous system. Although not essential in practicing the invention, it is preferred to. select an ethylenic co-monomer that is capable of homopolymerization into polymers which are self-dispersible, and preferably soluble, in water with appropriate stirring.

To date the optimum results have been obtained with copolymerizable mixtures which polymerize or set up to a gel in aqueous media, but those which polymerize to form rigid solids rather than gels are also operative in this invention. The swollen gels, of course, contain water but are not self-dispersible in water; and after drying they swell again upon rewetting to their original condition in which they are substantially impermeable to the passage of water and other inert liquids.

The following examples are merely illustrative, and it is not intended that the scope of the invention be limited to the details therein set forth. All parts are given in terms of weight, and the soil is in the air dry condition unless otherwise set forth.

Examples 1-18 Aqueous solutions of various monomeric acrylic acid derivatives, alone or in combination, are mixed With small amounts of methylene bisacrylamide. A suitable catalyst is added, and the catalyzed compositions are mixed with soil and permitted to polymerize at about 20'25 C. When methylolacrylamide is used, acid or alkali is added to the aqueous solution thereof to adjust its pH to about 4 or 11 in order to bring about condensation of the methylol groups. However, this condensation is merely an optional feature, as adequate cross-linking of the polymerizate for the present purposes is obtained with the methylene bisacrylamide. The results observed are tabulated below.

4. Examples 19-22 10 screen of approximately 50 mesh size immediately below a plate containing a plurality of one-quarter inch diameter holes. The drain connection at the bottom of the cylinder is closed for one hour while the composition is polymerizing. Then the condition of the polymerized 15 mass is observed. Later, 100 cc. of Water is introduced into the top of the cylinder and a pressure of 100 lbs. per square inch is applied at the top for a period of 30 minutes with the bottom drain line open While collecting any liquid discharge. The permeability of the stabilized soil composition under pressure is thus proportional to the amount of material discharged (water loss) at the bottom while the sample is under pressure. This test is a modification of that described in American Petroleum Institute Specification RP29, Section V, page 17, 1950, for determining the efiiciency of various agents in preventing lost circulation of oil Well drilling muds through porous strata.

In order to demonstrate the efiicacy of the present com- Oomposition Stability Resin Monomer Catalyst Soil Example Water,

' Per- After aging 16 After adding aged por- Per- Potassium Sodium Percent hours, 2025 0. tion to excess water Type cent Persnlfate, Bisulfite, Type cent Percent Percent 1 ;gg;{g;g3gg ;fgg 8- 0.11 0.05 Kaollnite- 40. 51 42.40 Toulgg, flexible No change. so 1 2 {fi i g g'f gg ag 0.1 Sand 80.0 9. 9 Hard solid Does not disintegrate.

Acry m 16:5 3 {g l 5 5g 0.2 Kaolmite- 00. 7 1s. 4. Tough, hard. SOlld. Insoluble.

a 0mm acry a e Acrylamide 2. 77 a 4 l l a )13 0.10 ...do 66. 7 22-0 H r solid 515 2151 tough. rubbery Methy e116 7 iacry ami e V 6 hfigggglgkggfgggfgE 33 0.14 0.05 Sand 71. 43 16.31 Hard mass Dgestntot dissolve or 1s m egra e. {pgggglggg gggg ggg- 1% 0.11 0.04 Kaolinite- 50.34 34.20 gugll sl gl lty No change.

8X1 980 1 Calcium acrylate 10.50 x h 7 g i sc qggg 0.12 0.03 Sand 66. 67 22.13 Hard sol1d Does not disintegrate a (311.1111 1 8- {Mcthylol acgylamide 4. 55 0.10 0.03 Kaolinite. 67. 50 21. 27 Hard, tough solid. Insoluble and rubbery.

eastern 212 a 0111 I 9 {ficrylamidegiTHE... g. 52 0.12 -do.. 66.67 22.05 Hard solid Stable, rubbery solid.

ethylene iacry am e .12 10 {f i jgfij i ff ig- 0.12 0. 03 Sand 00'. 01 22.03 ..-.-do Insoluble and rubbery. 11 {fii i gf g fifig g 0.10 0. 03 Kaolinite- 57.14 33117 .--d0 Stable, rubbery. Calcium acrylate 9: 26 1 I 12 {gfi i 0.09 0.03 do 51.13 33.26 Toslggadflexible Tough, flexlble solid.

a 0mm acry a c 13 {Methylene diacrymmid 47 0.10 0. 03 ...d0 51.14 33.20 .-d0 D0.

Composition Stability Resin Monomer Catalyst Soil After aging 16 After adding aged Example Ammoni- Sodium hours, 20-25" 0. portion to excess water Type Perum Thio- Type Pcr- Water,

cent Persulfate, sulfate, cent Per- Percent Percent cent 3- 0.10 0.10 Ventura Clay- 38.04 50. 00 Hard S0110 Does not disintegrate.

0.0 0.0 Connecticut 26.8 02.5 do Do. 5 Topsoil. 0.5 0.9 0.9 do 63.5 35.7 Flgxibe, tough Do.

' 0 1 g- 0.10 0.10 X-glct (Native) 50.00 48.80 sungel Do. Acrylamide 0. 027 b 18 {Methylene bisacrylamide 0' 033 0.066 0.198 Kaolmlte 33.0 66.0 Flfiglilgsgfidh Do.

positions over those which are unpolymerized, Comparative Examples A-D are included. Substantially no sealing efiect is produced in contrast with the high impermeability obtained in the illustrative numerical examples.

1 6 Example .24

Example 23 is repeated with the following composition:

Example 22 shows that the compositions of the present Parts by weight invention are effective when they are polymerized in situ Trenton sandy loam (oven dry basis) 100.0 in porous rock formations, inasmuch as 175 grams of Acrylamide T 2.85 crushed granite 0.25 to 0.375 inch particle size is stirred Methylene bisacrylamide 0.15 into the soil-resin mixture prior to depositing the resulting Ammonium persulfate 0.15 slurry in the test cylinder. Sodium thiosulfate 0.15

Composition Stability Resin Monomer Catalyst Soil 0 I Water, After aging Water Loss, cc./30 Example Ammo- Sodium Per- 1 hour minutes at 100 p. s. i.

Type Pernium Per- Thio- Type Percent cent sulfate, sulfate, cent Percent Percent {fig g 'j fg igk 0.8 0.3 Kaolinite 30.3 01.4 Stifisolid. 2.0.

Acrylamide Methyleqebmcrylamme 0 0.8 --...d 32.8 65.0 sl r y 00.0. {fi g ig g 3:; 0.9 0.9 Bentonlte 6.1 37.4 Rubberysolid 5.0. B {fi f% 4 1.0 1.0 0.3 91.7 Slurry 951iuk3dmin. then 0011 ea e gas. 21 {Methylene 0.5 0.5 Ool nncctiifut 31.3 62.5 Thick 50110-. 13.5.

Aerylamide opso o bmcrylamide 0.5 0.5 ..-.-do 33.0 00.0 Slurry 130-;gan dryinlO 22 {Acrylamide 0 s 0 s (ra e1 an d) 7 01 5 Th! k 110 ra ates lllethlyleng bis-acrylamide 0.3 g 2 5 c so 1) 0.8 0.8 .-do 32.8 05.0 Slurry 150-ran dryinb {Methylene bls-acrylamide i I minutes.

Example 23 Using the same shearing test procedure, the following Parts by weight results are obtained: Salt Lake silt loam (oven dry basis) 100.0 Acryl mide Ultimate Shear Methylene brsacrylamide 0.1 NormalLoad S 1 Strength Ammonium persulfate 0.1 A Solium thiosulfate 0.1 4 g The monomer and catalyst components above are dis- 4 4 solved in water and added to a sample of the air dry soil :2 18 with all particles finer than 20 mesh. Sufficient extra fig gag water is added to render the mass plastic for ready molding in brass tubes; these tubes are exactly the same diameter as the chamber of the shear machine. The samples are kept saturated with water for at least 24 hours until shortly before testing and then allowed to drain. Similar soil columns are molded from the same soil with water only added to serve as controls. The soil columns are pushed from the sample tubes into the shear machine and the machine is then loaded with suitable normal loads which are allowed to act for 15 minutes before the shear load is applied over 3 to 5 minutes by loading a water tank to ultimate failure of the samples. The collected data are:

Ultimate Shear Strength, p. s. i. Normal Load, p. s. i.

Control Treated Soil Again, a striking increase in shear strength isobtained with an extremely small amount of the soil-treating agents used in the present invention.

Another polymerization product using the same type of soil with one-third less of each of the same monomers is found to suffer no noticeable erosion'from a jet of water directed against it for'4 hours.

The unsaturated monomers above and. the catalyst components are dissolved in the water and poured into a transparent vertical cylinderof 1.5 inches internal diameter and about 10 inches height with a porous ceramic plate at the bottom. Next, theair dry soil is rapidly stirred into the solution while the porous plate is sealed off to prevent the passage of any liquid therethrough. It is noted that the soil is thoroughly impregnated with the solution and free of air pockets or voids. Gel formation at the top of the soil mass is observed after 10 minutes. Later, the cylinder is filled with water and the seal below the porous plate removed. After 45 minutes no water has passed through the soil mass and porous plate under atmospheric conditions. Next, .a compressed nitrogen Example 26 Example 25 is repeated using half the quantity of the same monomers and catalyst components. This mixture is allowed to stand overnight; then the test cylinder is filled with water. At atmospheric pressure, 49 minutes is required for cc. of water to pass through the soil composition and porous plate, and 3 minutes 34 seconds is required for the same quantity to drain through under a superatmospheric pressure of 5 p. s. i.

Example 27 Grams Long Island sandy soil 50.0 Allyl acrylamidopropyl dimethylammonium chloride 0.95 Methylene bisacrylamide 0.05 Potassium persulfate 0.01 Sodium metabisulfite 0.01

Water 19.0

Following the precedure of Example 25, the above materials are mixed in the vertical cylinder and allowed to stand overnight. Upon filling the test cylinder with water, the permeability of the sample is found to be greatly reduced from that of the control.

Example 28 Grams Long Island sandy soil 50.0 Nonaethylene glycol monomethacrylate 1.0 Methylene bisacryl'amide 0.05 Ammonium persulfate e 0.005 Sodium metabisulfite 0.005 Water 20.0

The procedure of Example 25 is duplicated with the above composition. After standing for 2.5 hours, the resulting mass is found to be impermeabilized to the extent that no water passes through it at atmospheric pressure over a period of minutes or under a pressure of 5 Example 29 Grams Long Island sandy soil 50.0 N-vinyl-Z-pyrrolidone' 1.6 Methylene bisacrylamide 0.4 Ammonium persulfate 0.02 Water 20.0

Example is repeated with the above ingredients standing overnight in the test cylinder. A low degree of permeability is obtained.

Example 30 Grams Long Island sandy soil 50.0

The procedure of Example 25 is followed in general, but the soil is mixed and saturatedwith an aqueous solution of the following content by weight:

Percent Vinyl acetate 2.0 Methylene bisacrylamide 0.2 Ammonium .persulfate 0.5 Sodium thiosulfate 0.5

After standing overnight, the resulting mass displays low permeability to water.

Example 31 Grams Silt 50.0

Again the procedure of Example 25 is repeated, except that the silt is thoroughly mixed and saturated in the test cylinder with a sufiicient quantity of an aqueous solution containing the following percentages by weight of Vinyl sulfonic acid 19.0

Methylene bisacrylamide 1.0 Ammonium persulfate 1.0 Sodium thiosulfate 1.0

After standing for 16 hours, the silt composition is found to have an extremely low degree of permeability to water.

Any soil may be used as a constituent of the present composition including silt, sands, loams, clays, etc., both naturally occurring and those which have been processed by mining, washing, etc., such as bentonite, kaolinite and the like. Soil mixtures are also within the scope of the invention, including such materials as oil well drilling muds. Thus, the term soil is used herein in a broad sense and expressions such as ground and earth are employed to denote the solid surface of the earth and its interior.

Any copolymerizable composition containing an alkylidene bisacrylamide according to the above formula and an ethylenic comonomer of the type described may be employed in practicing the present invention to produce soil masses of decreased water permeability and/or improved load-bearing properties by conversion of the soil composition to a substantially water-insoluble state. This conversion appears to be brought about by an addition or vinyl type polymerization with cross-linking by the bisacrylamide' resulting in a three-dimensional structure.

In place of the -N;N-methylene bisacrylamide of the examples, any of the alkylidene bisacrylamides including dimethacrylamides corresponding to the above formula which are described and claimed in Lundberg Patent 2,475,846 or mixtures thereof may be used as crosslinking agents. Only slight solubility is required in view of the small amount used; therefore, this component may have a water solubility as low as about 0.02% by weight at 20 C. but a solubility of at least about 0.10% is more desirable for general purposes.

A wide variety of ethylcnic comonomers or mixtures thereof are copolymerizable with the alkylidene bisacrylamides; those having at least one C=C group and appreciably soluble in water are suitable for use in the present invention. The dangling bonds in the formula may be attached to one or more of many different atoms or radicals including hydrogen, halogens such as chlorine and bromine, cyano, aryl, aralkyl, alkyl, and alkylene with or without solubilizing groups attached to these hydrocarbons. In addition, the substituents in the ethenoid may comprise one or more hydrophilic groups including formyl, methylol, polyoxyalkylene residues and quaternary ammonium salt radicals,

O-i (OH),

OOCH, OOCCHs; SOsX, where X is H, NH4, an alkali metal or an alkylamine; CONR-z and -CH2CONR2, where each R is hydrogen, alkylol, lower alkyl or a polyoxyalkylene radical; and -COOR and -CHzCOOR', Where R is a H, NH4, alkali metal, alkaline earth metal, organic nitrogenous base, alkylol, lower alkyl or polyoxyalkylene radical. An extremely large number of combinations and permutations of the various suitable substitu'ents makes it impractical to list more than a few relatively speaking for illustrative purposes. The water solubilityof these substances is known to depend chiefly on the number and type of hydrophilic and hydrophobic radicals therein; for example, the solubility of compounds containing an alkyl radical diminishes as the length of the alkyl chain increases and aryl groups tend to decrease water solubility whereas the aforesaid hydrophilic substituents all tend to impove the solubility of a given compound in water. Accordingly, the comonomer should be selected according to conventional chemical practice from those containing sufficient hydrophilic radicals to balance any hydrophobic groups present in order to obtain the requisite water solubility of monomer.

Among the water-soluble ethenoid monomers, those containing an acrylyl or methacrylyl group are especially recommended. These areexemplified by N-methylol acrylamide, calcium acrylate, and methacrylamide; and theoptimum results have been obtained with acrylamide. Among the other suitable ethenoid compounds are acrylic acid; other N-substituted acrylamides such as N- methyl acrylamide, dimethylaminopropylacrylamide, N-

ethylol acrylamide, N-3-hydroxypropylacrylamide; acrylonitrile; saturated alkyl esters of acrylic acid, i. e. methyl acrylate, ,B-hydroxyethyl acrylate; ethylene glycol and polyethylene glycol acrylates, as exemplified by the re action product of fi-hydroxyethyl acrylate or acrylic acid with about 1 to about 50 mols or more of ethylene oxide;

salts of acrylic acid, i. e., magnesium acrylate, sodium acrylate, ammonium acrylate, ethyl acrylate, B-methyl aminoethyl acrylate, guanidine acrylate and other organic nitrogenous base salts, as exemplified by diethylamine acrylate and ethanolamine acrylate; quaternary salts like alkyl acrylamidopropyl dimethylamino chloride; acrolein, fl-carboxyacrolein, butenoic acid; d-chloroacrylic acid; as well as methacrylic acid and its corresponding deriva tives. Maleic acid and its corresponding derivatives including partial esters, partial salts, and ester salts thereof; maleamic chloromaleic, fumaric, itaconic, citraconic, vinyl sulfonic, and vinyl phosphonic acids and their corresponding derivatives and mixtures thereof. Such derivatives and other suitable compounds include o h-dichloroacrylonitrile, methacrolein, potassium methacrylate, magnesium methacrylate, hydroxyethyl methacrylate, zinc ,B-chloroacrylate, trimethylamine methacrylate, calcium a-chloromethacrylate, diethyl methylene succinate,

methylene succindiamide, monomethyl maleate, maleic diamide, methylene malonamide, diethyl methylene malonate, methyl isopropenyl ketone, ethyl vinyl ketone, propyl vinyl ketone, vinyl formate, vinyl lactate, vinyl acetate, vinyl bromoacetate, vinyl chloroacetate, vinyl pyrroli'done, allyl levulinate, allyl alcohol, methallyl alcohol, diallyl carbonate, allyl lactate, allyl gluconate, di(,B-aminoethyl)maleate, di(methylaminoethyl)maleate, di(N,N-dimethyl fi-aminoethyDmaleate, sulfonated styrene, vinyl pyridine, maleic anhydride, sodium maleate, ammonium maleate, calcium maleate, monopotassium maleate, monoammonium maleate, monomagnesium maleate, methyl vinyl ether, N-aminoethyl malearnide, N-aminoethyl maleimide, alkyl aminoalkyl maleamides, N-vinyl amines, N-allyl amines, heterocyclic ethenoid compounds containing nitrogen in a tertiary amino group, and the amine and ammonium are salts of said cyclic compounds, N-vinyl acetamide, N-vinyl-N-methyl formamide, N-vinyl-N-methylacetamide, N-vinylsuccinimide, N-vinyl diformamide, N-vinyl diacetamide, vinyl sulfonyl chloride, vinyl sulfonic acid salts, vinyl sulfonic acid amides, vinyl oxazolidone, allyl amine, diallyl amine, vinyl methyl pyridinium chloride, and allyl trimethyl ammonium chloride to name only a few of the operative compounds.

Due care should be exercised in handling any toxic compounds such as monomeric acrylamide.

The use for soil stabilization of certain polymers and copolymers of methylol acrylamido derivatives and cozinc acrylate, fi-amino- -chloroacrylic acid;

polymers of acrylamido derivatives, either methylolatedj or not, with monovinyl compounds is described and claimed in the cop ending application of oneof the present inventors, Russell L. Morgan, with James K. Dixon, Serial No. 224,842, filed May 5, 1951, entitled Soil Stabilization.

Polymerization of the vinyl groups of the compounds.

February 1, 1951, now U. S. 'Patent 2,751,374.- Polymerization has also been catalyzed with a reducing agent 1 alone. A mixture of the two materials in a redox system in quantities corresponding to their oxidation-reduction equivalents does not apear necessarybut may be desirable for some purposes.

The invention is not limited to any particular quantity of catalyst, but in general more than about 0.1% based on the weight of polymerizable monomers is desirable.

The time of gelation or polymerization is related to the amount of catalyst employed, and the induction period may be reduced within limits by increasing the amount of catalyst. Different soils also cause a wide variation in the time required for the soil composition to set up as do variations in temperature. For most purposes, a 15- to 30-minute induction period in the soil is suitable. For

best results, the gelation or polymerization time should be determined on the actual site by mixing one or more small trial batches above the ground where the time can be observed. While core drilling might also be employed for the same purpose-in connection with injection treatments, this would be considerably more expensive than the treatment mentioned above. With acrylamide and methylene bisacrylamide as the comonomers, it is suggested that about 10% by weight each of ammonium persulfate and sodium thiosulfate be introduced to catalyze the first trial batch, and the setting time be adjusted by doubling or halving the amount of catalyst until a satisfactory induction period isobtained. The same procedure may be used with other comonomer combinations. It may also be desired to employ non-metallic equipment or equipment having non-metallic coatings or linings, inasmuch as there is reason to believe that certain metals and alloys such as iron, brass, etc., have an accelerating effect which may cause premature polymerization. While this invention is not bound to any particular theory, it is believed that the solution of polymerizable monomers penetrates into substantially all pores of the soil particles and the exterior voids between the particles and sets to a three-dimensional copolymer. Such copolymers in the soil are equally impermeable to water and. otherinert liquids both wet and dry.

Certain redox systems (e. g., chloric acid-bisulfite) require acid conditions, and others operate best under acid conditions. Hence, in such cases polymerization below pH 7 is preferred. If acid polymerization is contemplated, any desired acidic material including sulfuric acid, hydrochloric acid, phosphoric acid, diammonium hydrogen phosphate, ammonium chloride, ammonium sulfate, etc., may be used for this purpose. In some cases, it may be desirable to use organic acids; but since they are more expensive, this is generally not an economical procedure.

However, acetic acid, oxalic acid, tartaric acid, phthalic anhydride and other acids may be used. While the quantities of acid employed may be varied widely from very small amounts which will produce a barely acid reaction,

11 itis often preferable that the pH be relatively low and of the order of 3.5 to 4.

In thecase of alkaline soils, it is possible to use a catalyst system comprising an amine as the activator for the vinyl polymerization. Examples of activators for peroxy-type catalysts such as persulfates and polyamines, i. e'., diethylene triamine, tetraethylene pentamine, etc., triethanolamine, dimethylaminopropionitrile, dimethylamino'ac'etonitrile, etc The polymer formation of a particular resin may vary-depending upon whether polymerization is effected in'the presenceof acid or alkali, and this factor should also be considered'in determining the polymerization conditions.

The-ratio ofpolymerizable material, which will comprise from about to about 30% alkylidene diacrylamid'e, and preferably about 3 to based on total polymerizable material, to soilmay be varied widely, but generally should be within the range of about 3 to about 200 partsby weight of soilto'l part by weight of polymerizable' material. The preferred range is between about and'about 100 parts of soil per part of comonomers. Ordinarily, the polymerizable material is dissolved in water to form a solution which is mixed with the soil. The concentration of the solution and the quantity used maybe regulated so that the concentrationof water in the final mixture of soil and stabilizing components varies anywhere between about 5% and about by weight, depending primarily on the type of soil. Sand, for ex ample, requires much less water than do certain of the clays. The proportion of water used determines to some U extent the properties of the resulting stabilized soil. It appears that the optimum conditions for polymerization are realized with at least sufficient water present to saturate'the soil, that is, to fill all voids between soil particles and pores therein with the solution of mixed monomers, at the'desired degree ofcompaction when polymerization occurs. Theinvention, however, is not limited to saturated soil compositions, as substantial advantages are. obtained with only partly saturated soil masses.

Compaction or densification of the soil composition helps decrease the Water permeability of the resulting product and has an even greater effect in enhancing the strength and load-bearing qualities of the resulting material. These effects may be due entirely or in part to the elimination of voids or air pockets from thesoil mass. The polymerizable material may be incorporated with the soil in any desired manner, as for example, by mixing in a revolving drum. A satisfactory method, for example, comprises premixing the soil and monomer and adding to the mixture a solution of the catalyst in water. Another method of application which may sometimes be employed is spraying an aqueous solution or dispersion of the polymerizable material onto the ground which it is desired to toughen. This expedient may not result in sufficient penetration in certain soils for some purposes, however, although the difficulty can often be at least partially overcome by plowing the soil either before or after spraying or simultaneously therewith. This can conveniently be done with the roto tiller type of plow having revolving tynes which thoroughly mix the top few inches of soil. For the reason given earlier, the treated soil is preferably compacted or densified by pressing, tamping, or rolling with a weighted roller prior to polymerization.

Still another method of application which may be employed involves injecting an aqueous solution of the mixed monomers together with a catalyst directly into the ground at'the site that is to be'stabilized or rendered impermeable to. water. For example, an earthen dam may be treated by simply driving perforate injection. nozzles or pipes into the side or top of the darn at appropriately spaced intervals without excavating any; earth; thenan aqueous mixture of the alkylidene diacrylamide and the ethenoid comonomer is pumped into-the ground under sufficient pressure. to force thernixture out into the soil for. a considerable distance from the injection pipe; Existing highway and railway road beds can be strengthened against erosion orwash-outs similarly. It is also possible to inject" two or three solutions in any order; for example, first-a solution containing the catalyst and then the other one or two solutions containing the polymerizable monomers together or separately in such a way that they mix for the first time at the desired location in the ground to be stabilized or impermeabilized. However, there is a possibility that an impermeable membrane or zone may be formed in certain instances unless the catalyst concentration and other polymerization conditions are selected or adjusted to provide a relatively long induction period. Such an impermeable membrane or zone, of course, is undesirable, as it tends to prevent complete diffusion or mixing of the constituents of the soil composition. ln a treatment of this nature, it is contemplated that the catalyst solution and the solution of the monomers impregnate exactly the same zones of subterranean soil, inasmuch as the heat liberated by the exothermic reaction in one portion of the zone containing mixed monomers or free radicals diffusing therefrom may induce polymerization in adjacent portions of said zone which contain no catalyst.

The compositions disclosed herein may be copolymerized at any temperature ranging from their freezing point up to the point at which any of the constituents decompose. Artificial heating may be employed, and this may be especially desirable in producing structural bricks, etc, to accelerate the polymerization and consequently the production of such units. However, it is usually highly desirable to avoid the expense of artificial heating and allow the polymerization to take place at naturally occurring or atmospheric temperatures and pressures. When deep subterranean injections are made as in treating oil wells, etc., due care should be exercised in adjusting the polymerization time, as described hereinabove for the higher temperatures encountered in the well.

The present compositions are especially useful for'seal ing porous formations along channels in the earth; for example, in plugging or blocking porous formations in an oil well through which a drilling mud is being expended as lost circulation. This treatment may be practiced in either of two ways. The polymerizable mixture of monomers and the catalyst may be mixed with available soil or spent drilling mudfor economy and pumped through the interior of the drill pipe for an appropriate interval; or if voids in the porous formation surrounding the bore are not too large, an aqueous dispersion or solution of the monomeric mixture and the catalyst alone may be pumped through the drill pipe into the porous earth to be sealed. The latter case is analogous to the injection methodsdescribed above, whereby two copolymerizable components of the three-component compositions are injected into a fixed body of soil, the third component.

The compositions described herein are also useful in the cementing of liners or casings in channels in the earth; for example in cementing an oil well casing in place after it has been lowered into the Well. This may be accomplished by pumping a slurry of soil (e. g., spent drilling mud), water, monomer mixture and catalyst down the interior of the casing and into the space between the exterior of the casing and the sides of the well. To insure against premature polymerization while the slurry is being put into place in a deep well, it is contemplated that the catalyst may be omitted from the slurry and later in troduced as an aqueous solution at the bottom of the well to initiate polymerization as it penetrates upwards through the soil mass, or by introducing the catalyst only at the bottom.

This invention has wide utility for any purpose in which it is desired to stabilize soil that is to cohereand strengthen soil masses, to impart high viscosity, solid or rubber-like properties, to minimize or substantially eliminate the permeability of soil to inert liquids such as water, and to increase its resistance to erosion by moving liquids. For example, the-compositions described herein may be used as linings for reservoirs, irrigation ditches adobe buildings, solid and hollow structural shapes such as soil bricks, blocks, and pipes which do not require firing or baking for adequate strength. Stabilized soil masses suitable for supporting sizable loads are usually rigid when dry and upon rewetting often become somewhat flexible or rubbery but do not disintegrate or weaken substantially. In preventing cave-ins and slides and reducing the amount of earth to be removed in excavating operations, the injection method is the simplest manner of forming the soil compositions and a relatively light treatment at the periphery only of the excavation is recommended in order to avoid hardening the ground to the stage where digging becomes diflicult, especially in the center of the excavation where stabilization serves no purpose. An outstanding advantage of the present invention is that soil, the major component of the composition, is available at the site and only the components of minor weight need be transported.

In order to insure sufiicient strengthening of any given section of ground for the support of heavy weight, a surface of from about 1 /2 inches to 6 inches of soil treated according to the process of the present invention should be provided. The actual depth necessary will, of course, vary depending upon how fluid the soil is to begin with or, in other words how much solidifying is required.

What we claim is:

l. A composition of matter which comprises between about 3 and 200 parts by weight of soil and 1 part of a water-soluble copolymerizable mixture comprising between about 0.005 and about 0.3 part of a monomeric alkylidene .bisacrylamide of the formula:

in which I R(|J H is a hydrocarbon residue of an aldehyde and R is of the group consisting of hydrogen and methyl, and another ethylenic comonomer of at least about 2 percent by weight solubility in water at 20 degrees centigrade, which composition is convertible by a copolymerization reaction in the presence of a catalyst to a substantially waterinsoluble mass.

2. -A composition according to claim 1 in which the alkylidene bisacrylamide comprises N,N-methylene bis acrylarnide.

3. A composition according to claim 1 in which said ethylenic comonomer contains an acrylyl group.

4. A composition according to claim 1 in which said ethylenic comonomer comprises calcium acrylate.

5. A composition according to claim 1 in which said ethylenic comonomer comprises acrylamide.

6. A composition according to claim 1 in which said ethylenic comonomer comprises methylol acrylamide.

7. A composition according to claim 1 in which said ethylenic comonomer is further characterized by the capability of forming homopolymers which are self-dispersible in water.

8. A composition according to claim 1 in which the alkylidene bisacrylamide comprises methylene bisacrylamide and said ethylenic comonomer contains a radical of the group consisting of acrylyl and methacrylyl radicals and has a water solubility of at least about 5 per cent by weight at degrees centigrade.

9. A composition according to claim 1 in which the quantity of soil is between about 20 and about 100 parts by weight per part of the copolymerizable mixture.

10. A composition accordingto claim 1 which comprises a water-soluble oxygen-containing polymerization catalyst.

11. Aprocess of stabilizing soil which comprises contacting soil with both the bisacrylamide and the ethylenic comonomer as defined in claim 1 in the presence of water to produce the composition according to claim 1, and then converting such composition in the presence of a catalyst to a substantially water-insoluble state by a copolymerization reaction.

12. A process which comprises removing soil from the ground, mixing the loose soil with the bisacrylamide and the ethylenic comonomer as defined in claim 1 in the presence of water to produce a composition according to claim 1, compacting the composition and converting the compacted composition in the presence of a catalyst to a substantially water-insoluble state by a copolymerization reaction.

13. A process which comprises injecting the bisacrylamide, the ethylenic comonomer as defined in claim 1 and water into the ground to provide a composition according to claim 1, and converting the composition to a substantially Water-insoluble state in situ by a copolymerization reaction in the presence of a catalyst.

14. A process which comprises applying the bisacrylamide and the ethylenic comonomer as define-d in claim 1 to the surface of the ground in the presence of water to produce a composition according to claim 1, and converting the composition in situ to a substantially waterinsoluble state by a copolymerization reaction in the presence of a catalyst.

15. A process which comprises sealing a porous earth formation adjoining a channel in the earth which comprises injecting an aqueous solution of the copolymerizable mixture as defined in claim 1 into the porous formation to produce a composition according to claim 1, and converting the composition in situ to a substantially water-insoluble state by a copolymerization reaction.

16. A process which comprises depositing a polymerizable mixture as defined in claim 1 into the space between a casing and a channel in the earth in the presence of water, and converting the composition in situ to a substantially water-insoluble state by a copolymerization reaction to cement the casing in the channel.

17. A soil composition comprising a substantially water-insoluble product of the copolymerization of the polymerizable matter as defined in claim 1 and soil to pro vide a composition according to claim 1.

18. A soil composition of decreased water permea bility which comprises a substantially water-insoluble product of the copolymerization of the polymerizable matter as defined in claim 1 to produce a composition according to claim 1 said copolymerizable matter comprising methylene bisacrylamide and an ethylenic monomer of at least about 5 percent solubility in water by weight at 20 degrees centigrade and containing a radical of the group consisting of acrylyl and methacrylyl radicals.

19. A composition of matter which comprises between about 20 and about parts by weight of soil and 1 part of a water-soluble copolymerizable mixture comprising acrylamide and between about 0.005 and about 0.1 part of methylene bisacrylamide, which composition is convertible by a copolymerization reaction in the presence of a catalyst to a substantially waterinsoluble mass.

20. A soil composition substantially impermeable to water which comprises a substantially water-insoluble product of the copolymerization of the polymerizable matter in between about 20 and about 100 parts by weight of soil impregnated with 1 part of a copolymerizable mixture comprising acrylamide and between about 0.005 and about 0.1 part of methylene bisacrylamide, said copolymerization being conducted in the presence of a catalyst.

7 2 1. A process of stabilizing soil which comprises conta'ctin'g alkaline soil with the bi-s'acrylamide and the ethylenic comonomer as defined in claim 1 in the presence of water to produce the composition according to claim 1 and then converting such composition in the presence of a catalyst system comprising an amine selected from the group consisting of triethanoamine, diethylene triamine, tetraethylene pentamin'e, dimethylaminopropionitrile and dimethylaminoacetonitrile, to a substantially water-insoluble state by a copolymerization reaction.

References Cited' in the file of this patent Barker et al.: Impermeabilization of Soils by the Injection of Monomer Pairs to Norm Swellin'g' Copolymers (Thesis, Mass. Institute of Technology, 1953), page 9; 

1. A COMPOSITION OF MATTER WHICH COMPRISES BETWEEN ABOUT 3 AND 200 PARTS BY WEIGHT OF SOIL AND 1 PART OF A WATER-SOLUBLE COPOLYMERIZABLE MIXTURE COMPRISING BETWEEN ABOUT 0.005 AND ABOUT 0.3 PART OF A MONOMERIC ALKYLIDENE BISACRYLAMIDE OF THE FORMULA: 